KEYBOARD DISPLAY INTERFACE
Hardware Description :
Keyboard and display is configured
in the encoded mode.
In the encoded mode, a binary
count sequence is put on the scan
lines SL0-SL3.These lines must be
externally decoded to provide the
scan lines for keyboard and display.
A 3 to 8 decoder 74LS138 is provided
for this purpose. The S0-S1 output
lines of this decoder are connected
to the two rows of the keyboard.
And QA0 to QA7 is connected to 7
Segment Display